In the preparation and storage of foodstuffs, both raw and cooked, and both in the home and in the grocery store or supermarket, some manner of indication is desirable to indicate whether frozen items have previously been thawed. As will be apparent, such information is useful from health, safety, and nutritional standpoints. When it is considered that such items as blood, various medications, serums, culture plates, biologicals, etc., are also stored frozen, it not only is desirable to know that thawing has taken place, but essential to know such fact. Although the use of maximum-minimum thermometers can provide an indication that a frozen item had previously been thawed, the use of such apparatus with each and every item in the frozen food department of a grocery store or supermarket (or with each and every container of blood, drug, or other heat fragile item) is both totally impracticable and prohibitively costly.